正常的dfs

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:

    int dfs(TreeNode* root,int cnt)
    {
        if (!root) return 0;
        if (!root->left && !root->right) return cnt * root->val;
        return dfs(root->left, cnt + 1) + dfs(root->right, cnt + 1);
    }
    int pathSum(TreeNode* root) {
        return dfs(root,0);
    }
};